1. Field of the Invention
This invention relates generally to elastomers and more specifically, to elastomers having natural or synthetic rubber that are useful for elastomeric articles, including tires.
2. Description of the Related Art
Rubber elastomers are often cured using either a sulfur curing system or a free radical cure system. Of the free radical curing systems, the systems that utilize organic peroxides as the free radical generator are the most common and well known. Peroxide curing systems initiate crosslinking via free radical mechanisms using the organic peroxide as the curing agent. Known advantages of peroxide curing systems include, for example, the ability to cause crosslinking in lower compression set, better chemical and oil resistance, less discoloration, and better color stability with less staining.
Coagents have been used in peroxide curing systems in order to ameliorate the disadvantages while capitalizing on the desirable characteristics of free radical curing systems. U.S. Pat. No. 5,310,811 discloses the use of a free radical curing system and compares the effect of coagents on the cured elastomers. The coagents studied included trimethylol propane trimethacrylate, zinc dimethacrylate (ZDMA) and hydroquinone dimethacrylate. The effects of these coagents added separately to elastomer compositions were studied.
U.S. Pat. No. 5,506,308 discloses the use of a peroxide curing system that uses a precure inhibitor as well as zinc dimethacrylate (ZDMA). The precure inhibitor protects against scorch or prevulcanization of the elastomer and the unsaturated carboxylic metal salt during compounding.
Because of the benefits of using peroxide curing systems, research has continued to discover additional coagents and/or additional uses for coagents and peroxides that can improve the curing and the physical properties of elastomers.